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Can Fluent start a simulation from a negative time

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Old   November 23, 2008, 15:06
Default Can Fluent start a simulation from a negative time
  #1
Ted Chu
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Hi all,

I am trying to do a simple 2D wave tank simulation. A solitary wave will be generated and propagate from left to right. I am using the DEFINE_CG_MOTION udf on the left wall (as a wavemaker). The velocity profile in the udf is a hyperbolic secant function varying with time. In order to have the left wall to follow the profile, the simulation needs to start from a negative time. I was just wondering if Fluent can start a simulation from a negative time?

Thanks..
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Old   November 23, 2008, 16:12
Default Re: Can Fluent start a simulation from a negative
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Rogerio Fernandes Brito
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I donīt think so!

http://rapidshare.de/files/40979319/0_wave.rar.html
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Old   November 23, 2008, 16:43
Default Re: Can Fluent start a simulation from a negative
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Ted Chu
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Thank you Rogerio. I already have this tutorial. It uses sine function which starts at time 0 to generate waves. Do you know how to use sech function which starts at a negative time in Fulent?? Or, is there another way to get around??
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Old   November 23, 2008, 17:18
Default Re: Can Fluent start a simulation from a negative
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Rogerio Fernandes Brito
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I will talk with others researchers about it, īcause iīm new in Fluent.

Best regards,

Rogerio.
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Old   November 23, 2008, 19:58
Default Re: Can Fluent start a simulation from a negative
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Ted Chu
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Thanks Rogerio.. At the mean time, can anyone else help??
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Old   November 24, 2008, 16:49
Default Re: Can Fluent start a simulation from a negative
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CDE
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You can set Fluent's flow time using the text command: (rpsetvar 'flow-time 0.0)

Replace 0.0 with the the flow-time you require. I have never tried using this with a negative time so I don't know if it will do what you require.
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Old   November 25, 2008, 16:48
Default Re: Can Fluent start a simulation from a negative
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Ted Chu
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Thanks.. I am trying it now, but I got this message saying INVALID COMMAND [rpsetvar]. Don't know why....
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Old   November 25, 2008, 22:30
Default Re: Can Fluent start a simulation from a negative
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CDE
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did you include the brackets when inputting the command?

copy the command below exactly

(rpsetvar 'flow-time 0.0)
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Old   November 26, 2008, 07:00
Default Re: Can Fluent start a simulation from a negative
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Ted Chu
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No, I did not include the brackets. I copied the command line into the console window, then got that message.

I just tried it again, but no luck still getting the invalid command rpsetvar.

I am using Fluent 6.3.26 on Windows. Thanks...
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Old   November 26, 2008, 16:00
Default Re: Can Fluent start a simulation from a negative
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CDE
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you need to include the brackets....it won't work without them. Its a scheme command
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Old   November 26, 2008, 21:06
Default Re: Can Fluent start a simulation from a negative
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Ted Chu
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Thanks a lot CDE!!! It worked. Yes, now I can start the simulation from a negative time.

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